First successful run was around dusk on Saturday, 03 Sep 2005. Air was about 80 degF and moderately humid. Propane delivered at 20 PSIG (flow adjusted via needle valve), starting air at 30 PSIG, spark ignition. The engine was held in my new vise, clamped about halfway along the tailpipe.

MAIN PROBLEM ENCOUNTERED -

I finally had to add a 3-inch pipe extension to get it to sustain, making the total length 24.5 inches.

STARTING -

There is a strange 'sputtering pulsation' mode with starting air and low fuel levels. Sustaining operation is not possible until you allow enough fuel flow to smooth this out - as soon as you have that level of fuel flow, you can add just a little more, kill the starting air and the engine is running.

RUNNING -

Perfectly smooth running was observed over a wide range of fuel flows. I never did reach rich extinction with my regulated setup (20 PSIG max. available pressure and needle valve wide open). I have never been able to kill an FWE engine with too much fuel. This leads me to think that either the regulator, the needle valve and/or the 1/8-inch copper fuel line is too restrictive.

Very high temperature all over the chamber, and it comes to red heat very quickly (due, no doubt, to the thin steel used). The front dome is very hot - even the spark plug shell reaches red heat after a minute or two! (I thought this would ruin the little CM-6 plug for sure, but apparently not!) There is no visible tailpipe radiation anywhere along the pipe (remember, though, that I'm getting pretty effective heat sinking from that vise).

There is very heavy flame ejection from the intake, due to the orientation of the intake pipe. Good internal and ejected flame colors, indicative of good lean combustion. Unlike what was seen in the 'Short Lady', there is no 'cold spot' observable anywhere on the chamber. 'White hot' spark plug electrode and rim observable through the intake (not through the tailpipe, due to the weird orientation of the chamber cone).

COOLING DOWN -

The chamber shell cools down quickly, as would be expected with such thin material. Amusingly, the heavy oval-shaped weld all around the intake tube stays hot a long time as a sort of stretched-out, red-hot 'halo' (no doubt to symbolize the purity of this design ;-) I'll try to get a picture of this, just for fun. After cooldown, there was no distortion of the chamber noted, and a uniform blue-black oxidation covered the entire cone and dome. The vise was hot for a pretty long time after the run.

CONCLUSIONS -

The Smooth Lady started easily and ran well after the embarrassing 3-inch length adjustment. I think the front dome of the chamber is running too hot, and I believe I should have used the severe turndown of the intake 'spout' as I showed in the intake detail plan. I would rather have a cold zone in the front than a red-hot spark plug (of course, the plug could be relocated elsewhere in the chamber and would still work, I'm sure).

Bruno - Did you observe anything like the 'sputtering pulsation' mode when starting the Fo Mi Chin II out at Burning Grape? I'm asking since the intake geometry / orientation of the Smooth Lady is somewhat similar. If not, perhaps this too is a symptom of the minimal intake 'spout' that I used. Does anyone know if a small Thermojet will demonstrate this effect during starting?

Well the sputtering pulseation would usually mean that the intake is not quite the right length, or that it is getting poor fuel mixing (or both). I doubt that it had anything to do with the intake spout.

I think you have also encountered that if the tailpipe is shorter than 17.5" the performance is crap, and too much shorter wont even run at all.

As for thermojets, at least the one I have been designing, they start almost instantly with forced air (if its even needed at all), and some will even start just by turning on the propane.

Eric

Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

Eric wrote:Well the sputtering pulseation would usually mean that the intake is not quite the right length, or that it is getting poor fuel mixing (or both). I doubt that it had anything to do with the intake spout.

Hmmm ... I could easily understand that explanation if it were "machine gunning" (bam-bam-bam-bam-bam...) but this is definitely pulsating in short bursts (brrrrp-brrrrp-brrrrp-brrrrp-brrrrp...). Each little burst is clearly smooth pulsation - you know you're getting close to sustaining, and you can hear exactly what frequency your sustaining run is going to be!

It seems to me to be more like what Mark gets "jam jarring" his Dynajet with a spritz of alcohol, except here the fuel gets re-supplied after a split second's rest, and it goes again. Really interesting.

Larry Cottrill wrote:Bruno - Did you observe anything like the 'sputtering pulsation' mode when starting the Fo Mi Chin II out at Burning Grape? I'm asking since the intake geometry / orientation of the Smooth Lady is somewhat similar.

Larry, I am embarrassed to say that I was so excited starting that engine that I just don't remember! There I was, in California, half a planet away from home, surrounded by pulsejet enthusiasts and about 15 different pulsejets, and trying to start a brand new type of engine. I couldn't even remember what my name was. Sorry about this shameful lack of scientific rigor. Next time, I'll try to concentrate harder.

Running 'full grease' (or as near as I can get it), the intake flame comes straight out for a little over an inch, then mysteriously flattens down against the tailpipe and wraps itself around it - tres Coandaesque! Of course, this is only observable in near-darkness, but I tried to get a photo of it to show what I mean (photos available in just nine days ... stay tuned!). This was seen by clamping the vise onto the engine out on the rear half of the tailpipe, so the flow was not affected by the vise jaws. Quite amusing, at least to me. I haven't decided whether this would affect thrust or not, though I would guess it would not be anything very significant.

I also tried to get a photo of the 'hot halo' as the engine cooled, as mentioned above. Obviously, I ought to run the Fo Mi Chin II under the same conditions, to see if there is any similarity of these effects, due to the somewhat similar intake configuration. I have not run that engine since getting it back from Mike E a few weeks ago.

I guess I have forgotten to mention that the finished weight of my Smooth Lady is a hair under 17 ounces with spark plug in place, and with my usual starting air / fuel tube combination. There are no engine mount lugs. Considering the amount of contiguous weld around the intake tube, this compares quite favorably, I think, to the Fo Mi Chin II's final weight of 15 ounces. Of course, I am not recommending that anyone else use 24 gauge material for the chamber (unless you are a fairly expert weldor and just want a challenging project!) - construction will be MUCH easier if ~1mm material is used, as in the original Short Lady prototype engines, but you will probably gain about 5 ounces in engine weight overall.

Larry Cottrill wrote:Bruno - Did you observe anything like the 'sputtering pulsation' mode when starting the Fo Mi Chin II out at Burning Grape? I'm asking since the intake geometry / orientation of the Smooth Lady is somewhat similar.

Larry, I am embarrassed to say that I was so excited starting that engine that I just don't remember! There I was, in California, half a planet away from home, surrounded by pulsejet enthusiasts and about 15 different pulsejets, and trying to start a brand new type of engine. I couldn't even remember what my name was. Sorry about this shameful lack of scientific rigor. Next time, I'll try to concentrate harder.

Bruno, I observed the sputtering on my first startups of Fo Mi Chin II, as well, but over a very small range. See my update on the 'Voice of Fo Mi Chin' thread.

The last run I did with Fo Mi Chin II showed no such effect, with the flame coming straight out and simply traveling rearward along the top of the pipe. The only big differences are the cross-sectional shape of the intakes and the fact that the Smooth Lady can run at a MUCH higher power level (with a LOT more visible gas ejection out the intake).

It's good to hear from you! You're one of the guys I sometimes think of in the "I wonder whatever happened to ..." category. What's going on these days?

I am very surprised at the difference in running the Smooth Lady vs the original Short Lady. I think the Smooth Lady is potentially a much better engine. The fuel setup is exactly the same in terms of the intake, and the intake is the same ID pipe, but I can easily drive the Short Lady to rich extinction while the Smooth Lady acts like I'm not even getting close, no matter how much I open up the valve. I think that the 1/8 OD copper is acting as a restriction for the new engine, not so in the original. Even pressurizing the propane line to 20 PSIG, this still holds.

I think Eric's appraisal of trying to aim the intake flow is right, at least mostly: I disagree with him that the pipe protruding into the chamber is inherently a lot of the problem (the Smooth Lady does that, too), but I think he's right that bending the flow around has a lot more impact than I thought - the secret is, I think, delivering the flow forward right into the pressure antinode. Maybe that's the magic key - if so, no wonder the basic Melenric design was so good (supposedly)!

Dear Larry.
Another nice little motor, well done.
I wonder if an induction pipe augmenter can be added just by welding a single strip of sheet metal onto the tailpipe, in much the same way as the induction pipe?

Graham C. Williams wrote:Dear Larry.
Another nice little motor, well done.
I wonder if an induction pipe augmenter can be added just by welding a single strip of sheet metal onto the tailpipe, in much the same way as the induction pipe?

Best Regards
Graham.

Graham -

Thanks much. However, as discussed in my newer thread ('Numbers and Disappointments') on this forum, I don't seem to get any thrust out of her. Just a fueling geometry problem, or something much more structurally fundamental, as Eric believes? I'm not sure what to think ...